1. Field of the Invention
The present disclosure relates to a method of sensing touch, more particularly, to a display device including an optical sensing frame, which can detect multi-touches by locating an infrared camera sensor in a second corner of a liquid crystal panel, with a waveguide unit having at least two layers configured of light receiving and emitting layers, and a method of detecting touches.
2. Discussion of the Related Art
In general, a touch panel is one of elements which forms an interface between users and telecommunication devices using a variety of displays. A user may touch a screen of the touch panel by using a pen or his/her finger and he/she may interface with the telecommunication devices.
Such panel is an input device which can be used by people of all ages and sexes, because they only have to do touch a button of a display with their fingers to use the touch panel communicatively and intuitively. As a result, touch panels have been applied to various fields, for example, certificate-issuing devices used in banks or public offices, various medical apparatuses and guide devices used in sightseeing guides and traffic system guide and devices used in important organizations.
Such touch panel may be categorized into a resistive type touch panel, a micro capacitive touch glass, an ultrasonic wave glass and an infrared type touch panel, based on a touch recognition type.
First of all, the resistive type touch panel is configured of two transparent layers having conductivity. A bottom layer is formed of glass having conductive material coated thereon and a top layer is formed of film having conductive material coated thereon. The two layers are spaced apart a predetermined distance by a micro-printed spacer and are electrically insulated from each other. According to this resistive type touch panel, a predetermined voltage is applied to the two layers having the conductive materials respectively coated thereon. When a human finger or a touch pen touches the top layer in this state, resistance of the top layer (X axis) or the bottom layer (Y axis) may change according to the location of the touch. At this time, predetermined points of X and Y having changing resistive values are computed by a controller and the controller displays coordinates on a monitor or data is inputted.
The micro capacitive touch glass is configured of a transparent glass sensor having a thin conductor coated thereon. Because of that, an electrode pattern is precisely printed along an edge of a conductor layer and a transparent glass protection coating layer closely contacts with the conductor layer to protect and cover the sensor. According to this micro capacitive type touch panel, a voltage is applied to a screen and the electrode pattern forms a low voltage field on a touch sensor surface by using the conductor layer. When the human finger touches the screen, minute currents may be generated at touch points. The distance of the current flow from each corner is in proportion to the distance from the corner to the human finger and a touch screen controller computes the proportion ratio of the current flow to detect the touch point.
The ultrasonic wave touch glass is configured of 100% glass and it is not affected by surface damage or abrasion, compared with the other types of touch panels where surface damage or abrasion would terminate a usage life of a highly priced touch screen. A touch screen controller transmits an electric signal of 5 MHz to a transmitting converter configured to generate ultrasonic waves and reflected rays allow the generated ultrasonic waves to pass a panel surface. According to such ultrasonic wave type touch panel, in case a user pushes a touch screen surface, a part of the ultrasonic waves passing a touch point is absorbed by the user. A received signal and a lost signal in a digital map may be immediately identified by a controller and a coordinate value of the point where a change in the signal occurred may be calculated accordingly. This process may be independently implemented with respect to the X and Y axes, respectively.
The infrared type touch panel uses a property of an infrared ray that an infrared ray will go straight. The infrared ray is cut off and fails to go straight when meeting an obstacle. A point receiving pressure from the user's touch may cut off infrared rays emitted along the horizontal and vertical directions, and X and Y coordinates of the points where the infrared rays are cut off are read and sensed. Thus, the infrared type touch panel identifies the touch point by determining the cutting off of infrared scanning beams. To form an invisible infrared matrix, an infrared ray beam is emitted from a predetermined surface of each of X and Y axis and the emitted infrared ray beam is received by the other opposite surface in the infrared type touch panel.
Each touch panel type has different advantages, but the infrared type touch panel has been recently receiving attention because of its installation convenience and minimization of pressure received by the touch panel.
As follows, a conventional infrared type touch panel will be described in reference to FIG. 1.
FIG. 1 is a plane view illustrating the conventional infrared type touch panel.
As shown in FIG. 1, the conventional infrared type touch panel is configured to form a kind of an IR matrix. The panel may include a touch panel surface 14, a light emitting part 19 having a light emitting waveguide 10 formed in two sides near the touch panel surface 14, and a light receiving part 20 having a light receiving waveguide 16 formed near another two sides of the touch panel surface 14.
Here, lenses 12 and 15 connected with the light emitting and receiving waveguides 10 and 16 are provided in the light emitting and receiving parts 19 and 20, respectively, to transmit the lights emitted/received via the waveguides straight on the matrix. An LED light source 11 and a light splitter 18 are provided in a predetermined end of the light emitting waveguide 10 of the light emitting part 19 to transmit lights to the light emitting waveguide. A photo sensor part 17 configured to sense touch is connected to a predetermined end of the light receiving waveguide 16 of the light receiving part 20.
In this case, the photo sensor part 17 is a kind of a photo sensor array configured to measure coordinates and it has to be connected with the light receiving waveguide 16 for both X and Y axes.
The light source 11 and the photo sensor part 17 are provided in the ends of the light emitting part 19 and the light receiving part 20, respectively. The portion of the waveguide distant from the light source 11 and the photo sensor part 17 may be lengthened and the areas of the light emitting and receiving parts 19 and 20 may be enlarged.
According to another type of infrared type touch panel, different from the above structure, infrared cameras are located in two corners of a side of a liquid crystal panel, respectively, reflectors are provided in the other sides. After that, the infrared cameras triangulate the touch points to detect touch and touch points.
However, the conventional infrared ray type touch panel has following problems.
First of all, the light emitting part or the light receiving part which includes the waveguide and the lens has to be provided corresponding to the four sides of the touch panel. Accordingly, the configuration for sensing the touch has to be provided over all of the edge portions of the touch panel. As a result, the mechanical arrangement and the length of the electronic circuit line has to be complex and increased, only to generate an electromagnetic interference (EMI) in the display device which can affect the detecting of the touch implemented by the touch panel.
Second, the light receiving part and the light emitting part are each provided in two neighboring sides. As a result, the configuration has to be complex and the effective area happens to be reduced.
Third, in case of the infrared type touch panel including a full-reflective substrate, the corresponding lens has to be mold-injected. If the sizes have to be enlarged, there is a burden of fabricating a new corresponding mold. Therefore, this type may not be easily adapted to different sizes. In addition, an air gap is formed between the full reflection substrate and the display device, and accordingly image quality deterioration, external light scattering and the like may be generated, which can deteriorate the image quality. Also, the thickness of the device is increased because of the full reflection substrate and the air gap.
Fourth, the conventional touch panel would produce a ghost in case of multi-touches and therefore it is impossible to sense the multi-touches.
Fifth, in case the area of the touch panel is enlarged, the number of the pixels has to be enlarged correspondingly and the number of the waveguides and lenses has to be increased. In the module having the preset size, the effective area of the touch panel will be reduced. In case of the large area display device, it is difficult to apply the effective area efficiency of the display panel located under the touch panel having the light emitting part and the light receiving part located there below. Since the bezel of the display device is getting narrower recently, it is difficult to mount the above conventional touch module in the display device because of the volume and the weight.
Sixth, the module for the touch panel and the module to mount the liquid crystal panel therein are separately formed. Therefore, the separated touch module and the liquid crystal module have to be connected to sense a touch. In this case, the touch control unit and the liquid crystal module control unit have to be provided independently and an additional assembly is required.
Seventh, in case of the infrared sensing type using the triangulation, a dead zone in which a touch is impossible to detect, may be generated close to an edge area between the senses. Therefore, the predetermined area corresponding to the dead zone has to be provided in the edge area of the liquid crystal panel. In such case, the size and volume of the touch panel are increased and make a slim structure impossible.